使用jersey和maven开发RESTFul WebService

jersey是一种RestFul Webservice开发框架，作为JSR311的开源实现，替代了原有的基于SOAP的Web服务。jersey提供了更为简洁的API，提供了更为简洁的开发模式。

在实际应用中，将基于maven构建开发环境，主要其他工具包括：jersey1.8、Junit4、jersey-json。使用webservice访问实现对数据库的CRUD模拟操作。

pom.xml核心片段：

<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.7</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>com.sun.jersey</groupId>
			<artifactId>jersey-core</artifactId>
			<version>1.8</version>
		</dependency>
		<dependency>
			<groupId>com.sun.jersey</groupId>
			<artifactId>jersey-server</artifactId>
			<version>1.8</version>
		</dependency>
		<dependency>
			<groupId>com.sun.jersey</groupId>
			<artifactId>jersey-client</artifactId>
			<version>1.8</version>
		</dependency>
		<!-- Json -->
		<dependency>
			<groupId>com.sun.jersey</groupId>
			<artifactId>jersey-json</artifactId>
			<version>1.18</version>
		</dependency>
		<dependency>
			<groupId>com.owlike</groupId>
			<artifactId>genson</artifactId>
			<version>0.99</version>
		</dependency>

		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
			<version>1.2.14</version>
		</dependency>
		<dependency>
			<groupId>javax.ws.rs</groupId>
			<artifactId>jsr311-api</artifactId>
			<version>1.1.1</version>
		</dependency>
		<dependency>
			<groupId>asm</groupId>
			<artifactId>asm</artifactId>
			<version>3.2</version>
		</dependency>
	</dependencies>

编写Model类，用于传输数据，@XmlRootElement注解用于在以XML格式返回数据时，将Bean作为根节点：

package com.jersey.bean;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Student {
	private int id;
	private String name;
	private String dept;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getDept() {
		return dept;
	}
	public void setDept(String dept) {
		this.dept = dept;
	}
	public Student(){}
	
	public Student(int id, String name, String dept) {
		super();
		this.id = id;
		this.name = name;
		this.dept = dept;
	}
	
}

 使用jersey核心API构建WebService类。其中，list请求返回的数据格式是json，需要使用到genson的支持，这个工具可以将Java集合类绑定为特定的Json格式，从而使webservice访问请求响应json格式的数据。

package com.jersey.ws;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.ws.rs.DELETE;
import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.MediaType;

import org.apache.log4j.Logger;

import com.jersey.bean.Student;

@Path("/students")
public class RestWs {
	
	private static Logger logger = Logger.getLogger(RestWs.class);
	private static int index = 1;
	private static Map<Integer,Student> studentMap = new HashMap<Integer, Student>();
	
	public RestWs(){
		if(studentMap.size()==0){
			studentMap.put(index, new Student(index++,"Askok","SC"));
			studentMap.put(index, new Student(index++,"Kloki","KONER"));
		}
	}
	
	@GET
	@Path("{studentid}")
	@Produces({MediaType.APPLICATION_XML,MediaType.APPLICATION_JSON})
	public Student getData(@PathParam("studentid")int studentid){
		if(studentMap.containsKey(studentid)){
			return studentMap.get(studentid);
		}else{
			return new Student(-1,"NULL","NULL");
		}
	}
	
	@GET
	@Path("list")
	@Produces(MediaType.APPLICATION_JSON)
	public List<Student> getList(){
		List<Student> list = new ArrayList<Student>();
		list.addAll(studentMap.values());
		return list;
	}
	
	
	@POST
	@Path("add")
	@Produces("text/plain")
	public String addStudent(@FormParam("name") String name,
											@FormParam("dept") String dept){
		studentMap.put(index, new Student(index, name, dept));
		return String.valueOf(index-1);
	}
	
	@DELETE
	@Path("delete/{studentid}")
	@Produces("text/plain")
	public String deleteStudent(@PathParam("studentid") int studentid){
		logger.info("Delete student id at:"+studentid);
		
		Student del = studentMap.remove(studentid);
		if(del==null){
			return "failed";
		}else{
			return "Student:"+del.getName()+"has been deleted";
		}
	}
	
	@PUT
	@Path("put")
	@Produces("text/plain")
	public String putStudent(@QueryParam("studentid") int studentid,
										   @QueryParam("name") String name,
										   @QueryParam("dept") String dept){
		logger.info("Add sudent, it's id:"+studentid);
		
		if(studentMap.containsKey(studentid)){
			return "Can't add same student.";
		}else{
			studentMap.put(studentid, new Student(studentid, name, dept));
		}
		return "Student "+name+" has been added";
	}
}

注意， 

修改web.xml文件：

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
	<display-name>Archetype Created Web Application</display-name>
	<servlet>
		<servlet-name>jerseyws</servlet-name>
		<servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>

		<init-param>
			<param-name>com.sun.jersey.config.property.resourceConfigClass</param-name>
			<param-value>com.sun.jersey.api.core.PackagesResourceConfig</param-value>
		</init-param>

		<init-param>
			<param-name>com.sun.jersey.config.property.packages</param-name>
			<param-value>com.jersey.ws</param-value>
		</init-param>
		<init-param>
			<param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
			<param-value>true</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>jerseyws</servlet-name>
		<url-pattern>/rest/*</url-pattern>
	</servlet-mapping>
</web-app>

对GET和POST可以通过url访问及表单post提交进行测试。

对PUT和DELETE的客户端单元测试代码：

package test;

import javax.ws.rs.core.MultivaluedMap;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.BlockJUnit4ClassRunner;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.core.util.MultivaluedMapImpl;

/** 
 * @ClassName: TestPD 
 * @Description: (这里用一句话描述这个类的作用) 
 * @author hao1.yan
 * @date 2015年11月19日 下午3:25:58  
 */
@RunWith(BlockJUnit4ClassRunner.class)
public class TestPD {
	private static final String BASE_URL = "http://localhost:8080/jersey/rest/students";
	
	@Test
	public void testDelete(){
		Client client = Client.create();
		WebResource resource = client.resource(BASE_URL+"/delete/1");
		ClientResponse response = resource.delete(ClientResponse.class);
		System.out.println("Response with a status of:"+response.getStatus()+","+response.getHeaders().toString());
	}
	
	@Test
	public void testPut(){
		Client client = Client.create();
		WebResource resource = client.resource(BASE_URL+"/put");
		
		MultivaluedMap<String, String> queryParams = new MultivaluedMapImpl() ;
		queryParams.add("studentid", "4");
		queryParams.add("name", "Klossd");
		queryParams.add("dept", "newPL");
		
		ClientResponse response = resource.queryParams(queryParams).put(ClientResponse.class,"foo:test");
		System.out.println("Respone a status:"+response.getStatus());
	}
}

 整个Webservice开发完成后，使用的基准URL是BASE_URL所定义的值，在访问其他资源时，只需要追加特定的路径和参数即可。